Inclusion / crack in 17-4 stainless steel and 420 stainless steel 2

[tdomm]

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1430403351/tips/Cracking-1_nq71hy.bmp[/url]


I need some help

We have inclusions "cracks" in .250" bar stock we are machining. The inclusion is a black substance but we can not figure out what it is and is not all the way through the material. The material is round ground bar stock usually used in Swiss style machining.

thanks TDomm

 

[EdStainless]

In 420 it is probably MnS inclusions, commonly called stringers.
You can cut some samples and section them lengthwise and polish the surface, you will see the streaks.
As for 17-4 it should be very clean, unless this is low quality bar stock you should not see any inclusions.

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P.E. Metallurgy, Plymouth Tube

 

[Guest102023]

Sorry but I don't see anything other than a slit across the entire piece.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[mrfailure]

I can see a crack at the slit where the tip of the arrow points. This feature seems to follow the grinding marks, and is not the geometry I would expect of an inclusion. You would be best served if you polished this surface, then looked at wht this feature looked like. If the plane of the picture is perpendicular to the longitudinal direction of the bar (an impression I get from the picture), then you really can't tell anything regarding inclusions - you need to be looking at the longitudinal plane.